1. Field of the Invention
This invention relates to igniter elements and, in particular, to igniter dies formed using solid state manufacturing technology to provide igniter bridges on substrates.
Igniter dies find use in the initiation of reactive materials, i.e., pyrotechnic materials and/or explosive materials. Such igniter dies comprise a bridge of conducting or semi-conducting material disposed on a relatively non-conducting substrate. Typically, the bridge is configured as a rectangular solid with its smallest dimension being its height from the surface of the substrate. Larger pads of the bridge material are formed at the ends of the bridge to support electrical contacts for receiving electric current. In use, such dies are incorporated into initiation devices that also comprise a reactive material, i.e., a pyrotechnic and/or explosive material. The reactive material is pressed against the bridge and a small charge of electric current is passed from one pad to the other through the bridge, which vaporizes and initiates the reactive material. This initiation process is useful in various devices, e.g., squibs, detonators, rocket motors, etc.
In prior art igniter dies, the bridge and pads are formed on a planar substrate, i.e., one having a flat top surface, and so have a planar configuration.
2. Related Art
U.S. Pat. No. 6,105,503 to Baginski entitled “Electro-Explosive Device With Shaped Primary Charge”, dated Aug. 22, 2000, which is incorporated herein by reference as background material, discloses an electro-explosive device. The device comprises a silicon substrate (31) (FIG. 2) having, on the bottom layer, an electrical contact (33). On the top layer, a second electrical contact (38) is insulated from the substrate by a dielectric layer (34) except in the region where a cup-shaped bridge portion (37, 38) of the electrical contact lines a cavity (36) formed in the substrate. Reactive material is disposed in the cavity. By applying a potential from one contact to the other, current flow can be induced through the bridge portion and the substrate, and ohmic heating of the bridge portion of the top contact causes it to initiate the reactive material therein. The interface between the metallic bridge element and the silicon substrate defines a Schottky diode disposed in series between the electrical contacts.
U.S. Pat. No. 4,708,060 to Bickes, Jr. et al entitled “Semiconductor Bridge (SCB) Igniter”, dated Nov. 24, 1987, describes a device comprising a planar formation of semiconductor material (doped silicon 3, FIGS. 1A, 1B) disposed on a flat, non-conducting substrate 8 (sapphire). The semiconductor material is configured to have a thickness of about 1 to 10 micrometers (μm) and to define two large pads 14 joined by a small bridge 2 between them, the bridge having a length of up to about 200 μm. The pads are covered with metallic lands 11 so that electrical conductors can be connected thereto on either side of the semiconductor bridge 2. A reactive material 1 (FIG. 2B) is pressed against the bridge and may be initiated by passing a current through the conductors with sufficient energy to vaporize the bridge. In a specific embodiment, one bridge measured 17 μm long (from pad to pad), 35 μm wide and 2 μm thick, and had a resistivity of 60×10−4 ohm-cm. Another measured 100×67×4 and had a resistance of 3 ohms. In each of these prior art configurations, the igniter element has a planar configuration.
U.S. Pat. No. 4,976,200 to Benson et al entitled “Tungsten Bridge For the Low Energy Ignition of Explosive and Energetic Materials”, dated Dec. 11, 1990, discloses an ignition element comprising a tungsten bridge deposited on top of an insulating silicon bridge. The bridge is formed on a flat substrate and has a substantially flat configuration. In use, reactive material is pressed against the tungsten bridge and a small charge of electric current is passed through the bridge, which forms a plasma that initiates the reactive material.
U.S. Pat. No. 4,831,933 to Nerheim et al entitled “Integrated Silicon Bridge Detonator”, dated May 23, 1989, discloses an integrated circuit chip having a silicon substrate on which is formed a polysilicon bridge to which electrical contacts are connected. A glass tube is bonded to the substrate over the bridge and reactive material is packed in the bore of the tube and is thus guided into contact with the semiconductor bridge.